Prevalence of Mild Autonomous Cortisol Secretion in Adrenal Incidentalomas and the Significance of Subcentimeter Adrenal Nodules: A Single-Center Cohort Study

Abstract

<p><strong>Objectives:</strong> Adrenal incidentalomas (AI) have been increasingly detected with the widespread use of cross-sectional imaging. This study aimed to evaluate the clinical characteristics of AI and mild autonomous cortisol secretion (MACS) in an Asian population.</p><p><strong>Methods: </strong>Health records of consecutive patients referred to medical and surgical endocrine clinics from June 2012 to May 2019 for AI at a tertiary institution were analyzed. All patients underwent hormonal evaluation.</p><p><strong>Results: </strong>A total of 340 patients were included (52.1% males; median age 63 year old). Median followup was 7.8 years. 301 patients (88.5%) had unilateral AI and the median nodule size was 1.5 cm. Among 116 patients (34.1%) with functional nodules, MACS was the most common hormonal abnormality (23.5%). Among 50 patients with AI <1 cm, 8 (16%) were functional. Female sex (adjusted odds ratio (OR) 3.03, P < .001), larger AI size (adjusted OR 1.25, P = .010), hypertension (adjusted OR 2.74, P = .003) and prediabetes (adjusted OR 3.11, P = .028) were independent factors associated with MACS. The 5-year mortality of patients with MACS was significantly higher than those with nonfunctional nodules (10% vs 4.0%, P = .046) and had poorer overall survival (P = .043). Only 16/80 (20%) patients with MACS underwent adrenalectomy, all performed laparoscopically without complications. Upon follow-up, none of the patients in the surgical group had new-onset hypertension, glucose intolerance, hyperlipidaemia, and osteoporosis.</p><p><strong>Conclusions:</strong> MACS is the most common hormonal abnormality amongst AI. Hormonal evaluation should be considered for subcentimeter adrenal nodules. Minimally invasive surgery is a safe treatment for MACS which may reduce metabolic risks but seldom performed in this population.</p>